radiation may be scattered by its transmission through a medium containing particles. If the scatter results in no significant change in the wavelength relative to the primary radiation it is called elastic scattering. In cases where the scattering centres are small compared to the wavelength of the radiation the elastic scattering is called Rayleigh scattering and Mie scattering if this condition is not fulfilled.
Source:
PAC, 1985, 57, 1453. 'Nomenclature, symbols, units and their usage in spectrochemical analysis - V: Radiation sources (Recommendations 1985)' on page 1464 (https://doi.org/10.1351/pac198557101453)